WO2022088111A1 - Super-thick non-doped electroluminescent device based on thermally activated delayed fluorescent material, and production method therefor - Google Patents

Abstract

Provided is a super-thick non-doped electroluminescent device based on a thermally activated delayed fluorescent material. The device comprises a super-thick non-doped luminescent layer of the thermally activated delayed fluorescent material, and a hole injection layer, a hole transport layer, a barrier layer, the super-thick non-doped luminescent layer, an electron transport layer, an electron injection layer, and a cathode are sequentially formed by means of vacuum evaporation on an anode, so as to obtain the super-thick non-doped electroluminescent device based on the thermally activated delayed fluorescent material. The super-thick non-doped electroluminescent device based on the thermally activated delayed fluorescent material can emit green fluorescence (λ = 520 nm), the external quantum efficiency (EQE) of the device reaches up to 21.1%, the efficiency roll-off is small, and the device has advantages such as a low driving voltage and good luminescence stability.

Description

Ultra-thick undoped electroluminescent device based on thermally activated delayed fluorescent material and preparation method thereof technical field

The invention relates to the field of organic electroluminescent materials, in particular to an ultra-thick non-doped electroluminescent device based on thermally activated delayed fluorescent materials, which can be industrialized, has a simple preparation method and good performance, and a preparation method thereof.

Background technique

Electroluminescence (English electroluminescent), also known as electric field luminescence, or EL for short, is to generate an electric field through the voltage applied to the two electrodes, and the electrons excited by the electric field hit the luminescent center, causing electrons to transition, change, and A physical phenomenon in which recombination leads to luminescence. It is generally believed that under the action of a strong electric field, the energy of the electrons increases accordingly until it far exceeds the energy of the electrons in the thermal equilibrium state and becomes superheated electrons. During the movement process, the superheated electrons can ionize the lattice through collision to form electrons and empty electrons. Hole pairs, when these ionized electron-hole pairs recombine or the excited luminescent centers return to the ground state, emit light. Electroluminescence can be divided into high-field electroluminescence and low-field electroluminescence from the light-emitting principle. High-field electroluminescence is an in vivo luminescence effect.

A light-emitting material is a semiconductor compound, in which holes and electrons recombine in the light-emitting layer to form excitons, but most light-emitting materials suffer from the phenomenon of aggregation concentration quenching (ACQ), which requires low concentration doping in the host material as the light-emitting layer. It is difficult to precisely control the doping ratio, the co-evaporation preparation process is complicated, and the luminous efficiency is very poor in the case of high concentration doping, or even without doping the host material. At the same time, when the thickness of the light emitting layer is very thick, the turn-on voltage will also be very large. . Therefore, the non-doped light-emitting material can greatly simplify the process of preparing electroluminescent devices, and the ultra-thick light-emitting layer can solve the problem of large-area preparation of OLEDs in industry. TADF organic light-emitting materials can theoretically achieve 100% internal quantum efficiency without noble metals, which has become a research hotspot. TADF materials that have both non-doped properties and can emit light efficiently in ultra-thick thin films are rare, so it is simple to develop new ones. , High-efficiency non-doped TADF materials have become a current research hotspot.

technical problem

The invention discloses an ultra-thick undoped electroluminescence device of a chiral thermally activated delayed fluorescent material and a preparation method thereof. The chemical name of the chiral thermally activated delayed fluorescent material is 3,5-bis(9H-carbazole- 9-yl)-2,4,6-tris(3,6-di-tert-butyl-9H-carbazol-9-yl) benzonitrile, to solve the problem of difficult synthesis and preparation of delayed fluorescence luminescent materials, few types of materials and raw materials At the same time, it solves the problems of complex preparation process of electroluminescent devices and difficult preparation of large-area devices; especially, the OLED prepared by the ultra-thick undoped light-emitting layer of the thermally activated delayed fluorescent material realizes its EQE over 20%, low efficiency roll-off target.

technical solutions

The present invention adopts the following technical solutions.

An ultra-thick undoped electroluminescent device based on thermally activated delayed fluorescent material, comprising a thermally activated delayed fluorescent material undoped ultra-thick light-emitting layer; the light-emitting layer of the ultra-thick undoped electroluminescent device according to the present invention It is composed of its own thermally activated delayed fluorescent material; further, the thickness of the light-emitting layer of the thermally activated delayed fluorescent material is 50-200 nm.

The ultrathick undoped electroluminescent device based on thermally activated delayed fluorescent material disclosed in the present invention is composed of an anode, a hole injection layer, a hole transport layer, a blocking layer, an ultrathick undoped light-emitting layer, an electron transport layer, an electron injection layer Layer, cathode composition; specifically, indium tin oxide (ITO) is used as anode, bispyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7, 10,11-Capronitrile (HATCN) was used as a hole injection layer (HIL), 4,4'-(cyclohexane-1,1-diyl)bis(N,N-di-p-tolylaniline) ( TAPC) as hole transport layer (HTL), 1,3-bis(9H-carbazol-9-yl)benzene (mCP) as electron/exciton blocking layer (EBL), the thermally activated delayed fluorescent material Used as light-emitting layer (EML), 4,6-bis(3,5-bis(pyridin-3-yl)phenyl)-2-methylpyrimidine (TMPYPB) used as electron transport layer (ETL), lithium fluoride (LiF) is used as the electron injection layer (EIL), and aluminum (Al) is used as the cathode; further, the specifications of each layer of the organic electroluminescence device are: ITO/HATCN (10 nm)/TAPC (60 nm)/mCP (10 nm) nm)/TADF material(50-200 nm)/TMPYPB(45 nm)/LiF(1 nm)/Al(100 nm).

The invention discloses an ultra-thick undoped light-emitting layer for an electroluminescent device, which is a thermally activated delayed fluorescent material 3,5-bis(9H-carbazol-9-yl)-2,4,6-tris(3 , 6-di-tert-butyl-9H-carbazol-9-yl) benzonitrile alone.

The preparation method of the above-mentioned ultra-thick undoped electroluminescent device based on thermally activated delayed fluorescent material is as follows: vacuum evaporation of a hole injection layer, a hole transport layer, a blocking layer, an ultra-thick undoped light-emitting layer, An electron transport layer, an electron injection layer, and a cathode are used to obtain the ultrathick undoped electroluminescence device based on the thermally activated delayed fluorescent material. Vacuum evaporation is a conventional technique.

The thermally activated delayed fluorescent material of the present invention has the following chemical structural formula.

.

The preparation method of the above thermally activated delayed fluorescent material comprises the following steps: using 2,3,4,5,6-pentafluorobenzonitrile, 3,6-di-tert-butyl-9H-carbazole and 9H-carbazole as raw materials, The green thermally activated delayed fluorescent material is prepared by a continuous one-pot reaction; the reaction can be referred to as follows.

.

After the reaction is completed, the reaction solution is poured into water, and then a large amount of solid is obtained by suction filtration. The product is separated and purified by column chromatography (petroleum ether/dichloromethane, volume ratio is 4:1) to obtain the thermal activation delay. fluorescent material.

The invention provides a method for synthesizing and preparing a novel thermally activated delayed fluorescent material; and an ultra-thick undoped electroluminescent device based on the thermally activated delayed fluorescent material, which achieves the goal of having an EQE exceeding 20% and a low-efficiency roll-off; It is used to solve the problems of difficult synthesis and preparation of delayed fluorescent light-emitting materials, few types of materials, expensive raw materials, and quenching of aggregation concentration; meanwhile, it solves the problems of complex preparation process of electroluminescent devices and difficult preparation of large-area devices.

There are no special restrictions on the preparation method and other raw materials of the ultra-thick undoped organic electroluminescent device formed based on the thermally activated delayed fluorescent material according to the present invention. The organic thin film formed by the invention has high surface smoothness, stable chemical and physical properties and high luminous efficiency, and the formed ultra-thick undoped organic electroluminescent device has good performance.

beneficial effect

The beneficial effects of the present invention are as follows.

1. 3,5-bis(9H-carbazol-9-yl)-2,4,6-tris(3,6-di-tert-butyl-9H-carbazol-9-yl)benzonitrile provided by the present invention Thermally activated delayed fluorescence materials have the characteristics of twisted internal charge transfer (TICT), and at the same time have typical thermally activated delayed fluorescence (TADF) properties, 100% high fluorescence quantum yield (PLQY) and high thermal stability and other advantages, more importantly What is interesting is that this compound has no aggregation concentration quenching (ACQ) effect in the pure film state.

2. The ultrathick undoped organic electroluminescence device based on the thermally activated delayed fluorescent material provided by the present invention has the advantages of low driving voltage and good luminescence stability, and the external quantum efficiency EQE of the prepared device is as high as 21.1%, which is Efficiency rolls off at high brightness.

3. The thermally activated delayed fluorescent material provided by the present invention has few synthesis and preparation steps, readily available raw materials, simple synthesis and purification processes, high yield, and can be synthesized and prepared on a large scale. Organic electroluminescent devices based on it have good application prospects in the fields of large-area lighting and flat panel displays.

Description of drawings

Figure 1 is the hydrogen NMR spectrum of Compound A prepared in Example 1.

FIG. 2 is the carbon nuclear magnetic spectrum of compound A prepared in Example 1. FIG.

FIG. 3 is the mass spectrum of Compound A prepared in Example 1. FIG.

FIG. 4 is an efficiency diagram of the devices of Examples 1 to 4. FIG.

FIG. 5 is an efficiency diagram of a device of Comparative Example 1. FIG.

FIG. 6 is a graph of the efficiency of the device of Comparative Example 2. FIG.

Embodiments of the present invention

The raw materials involved in the present invention are all conventional commercial products, and the specific operation methods and testing methods are conventional methods in the field; especially the specific preparation process and the materials of each layer of the organic electroluminescent device based on the thermally activated delayed fluorescent material of the present invention are existing Techniques, such as vacuum evaporation, the vacuum degree is ≤2×10 ^-4 Pa, the deposition rate of functional layer is 2 Å/s, the deposition rate of host material is 1 Å/s, the deposition rate of LiF layer is 0.1 Å/s, the deposition rate of Al The deposition rate was 8 Å/s. The inventiveness of the present invention is to provide a new thermally activated delayed fluorescent material with non-doped properties, and the ultra-thick non-doped material can be used alone as a light-emitting layer of an organic electroluminescence device.

In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with the examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

The present invention provides an efficient green thermally activated delayed fluorescent material 3,5-bis(9H-carbazol-9-yl)-2,4,6-tris(3,6-di-tert-butyl-9H-carbazole- 9-yl) benzonitrile (compound A).

The structural formula is shown below.

.

Synthesis example.

The reaction formula is as follows.

.

The reaction is specifically as follows.

Add 3.50 g (12.52 mmol) 3,6-di-tert-butyl-9H-carbazole and 15 mL N,N`-dimethylformamide (DMF) to a 150 mL three-necked flask, add 0.26 g under ice bath conditions (10.83 mmol) NaH, and then stirred for 30 minutes under the protection of nitrogen to obtain a mixed solution. In a 150 mL three-necked flask, add 1.50 g (8.97 mmol) 9H-carbazole and 10 mL DMF, add 0.22 g (9.12 mmol) NaH under ice bath conditions, and then stir under the protection of nitrogen for 30 minutes to obtain a mixed solution; add the mixed solution to 30 mL containing 0.80 g (4.14 mmol) 2,3,4,5,6-pentafluorobenzonitrile in DMF, react at room temperature for 12 hours, then add the mixed solution, heat at 120 °C for 12 hours under nitrogen protection; then pour the reaction solution into In the water, a large amount of solid was precipitated, which was filtered with suction, and the product was separated and purified by column chromatography (petroleum ether/dichloromethane, with a volume ratio of 4:1) to obtain a green solid 3,5-bis(9H-carbazole-9). -yl)-2,4,6-tris(3,6-di-tert-butyl-9H-carbazol-9-yl)benzonitrile, which was compound A in 53% yield.

Fig. 1 is the hydrogen nuclear magnetic spectrum of the compound A obtained above; Fig. 2 is the carbon nuclear magnetic spectrum of the compound A obtained above; and Fig. 3 is the mass spectrum of the compound A obtained above. The structure detection of compound A is as follows.

¹ H NMR (400 MHz, CDCl ₃ ) δ 7.66 (d, J = 1.5 Hz, 4H), 7.26 (d, J = 7.4 Hz, 4H), 7.23 (d, J = 1.8 Hz, 2H), 7.10 (d , J = 8.6 Hz, 4H), 7.04 (dd, J = 8.6, 1.8 Hz, 6H), 6.93 (d, J = 8.2 Hz, 4H), 6.77 (dd, J = 11.0, 3.9 Hz, 4H), 6.61 – 6.55 (m, 6H), 1.35 (s, 36H), 1.12 (s, 18H); ¹³ C NMR (101 MHz, CDCl ₃ ) δ 143.83, 143.42, 143.24, 141.11, 138.18, 137.62, 136.91, 136.08 , 124.13, 123.99, 123.80, 122.77, 121.96, 119.99, 118.97, 116.67, 115.99, 115.33, 110.46, 110.40, 109.98, 34.21, 31.82, 31.57; MALDI-TOF MS (ESI, M/Z) CALCD for C _{91 H88N6 [} M ⁺ ]: 1264.71, Found: 1265.915.

From the above detection results, it can be known that the structure of compound A is correct.

The application effect of the compound synthesized in the present invention as a light-emitting layer in a device will be described below through application examples.

Example 1 Fabrication and performance evaluation of an organic electroluminescent device with 50 nm material A as the light-emitting layer.

The fabrication steps of the organic electroluminescent device with 50 nm material A as the light-emitting layer are as follows.

(1) Pretreatment of glass anode: select a glass substrate (3×3 mm) with an indium tin oxide (ITO) film pattern as a transparent electrode; after cleaning the glass substrate with ethanol, UV-ozone processing to obtain a pretreated glass substrate.

(2) Vacuum evaporation: vacuum evaporation of each layer is carried out on the pretreated glass substrate by vacuum evaporation method, and the treated glass substrate is placed in a vacuum evaporation chamber, and the degree of vacuum is ≤2×10 ^{− 4} Pa, the device structure is as follows: ITO/HAT-CN (10 nm)/TAPC (40 nm)/mCP (10 nm)/A (50 nm)/TMPYPB (45 nm)/LiF (1 nm)/Al (100 nm); the specific layer evaporation is a conventional technique.

(3) Device packaging: seal the fabricated organic electroluminescent device in a nitrogen atmosphere glove box with a water oxygen concentration of less than 1 ppm, and then cover the above-mentioned film formation with a sealing cover with epoxy UV-curable resin glass. The substrate is sealed by UV curing; the specific encapsulation is conventional technology.

Performance evaluation of organic electroluminescent devices with 50 nm material A as the light-emitting layer.

Direct current was applied to the fabricated organic electroluminescent device, and the luminescence performance was evaluated by using an integrating sphere; the current-voltage characteristics were measured by a computer-controlled Keithley 2400 digital source meter. The luminescence properties of the organic electroluminescent device were measured under the condition of changing the applied DC voltage. Device performance is shown in Table 1 and Figure 4.

Example 2 Fabrication and performance evaluation of an organic electroluminescent device with 100 nm material A as the light-emitting layer.

The fabrication steps of the organic electroluminescent device with 100 nm material A as the light-emitting layer are as follows.

(1) Pretreatment of glass anode: select a glass substrate (3×3 mm) with an indium tin oxide (ITO) film pattern as a transparent electrode; after cleaning the glass substrate with ethanol, UV-ozone processing to obtain a pretreated glass substrate.

(2) Vacuum evaporation: vacuum evaporation of each layer is carried out on the pretreated glass substrate by vacuum evaporation method, and the treated glass substrate is placed in a vacuum evaporation chamber, and the degree of vacuum is ≤2×10 ^{− 4} Pa, the device structure is as follows. ITO/HAT-CN (10 nm)/TAPC (40 nm)/mCP (10 nm)/A (100 nm)/TMPYPB (45 nm)/LiF (1 nm)/Al (100 nm); Plating is a conventional technique.

(3) Device packaging: seal the fabricated organic electroluminescent device in a nitrogen atmosphere glove box with a water oxygen concentration of less than 1 ppm, and then cover the above-mentioned film formation with a sealing cover with epoxy UV-curable resin glass. The substrate is sealed by UV curing; the specific encapsulation is conventional technology.

Performance evaluation of organic electroluminescent devices with 100 nm material A as the light-emitting layer.

Direct current was applied to the fabricated organic electroluminescent device, and the luminescence performance was evaluated by using an integrating sphere; the current-voltage characteristics were measured by a computer-controlled Keithley 2400 digital source meter. The luminescence properties of the organic electroluminescent device were measured under the condition of changing the applied DC voltage. Device performance is shown in Table 1 and Figure 4.

Example 3 Fabrication and performance evaluation of an organic electroluminescent device with 150 nm material A as the light-emitting layer.

The fabrication steps of the organic electroluminescent device with 150 nm material A as the light-emitting layer are as follows.

(1) Pretreatment of glass anode: select a glass substrate (3×3 mm) with an indium tin oxide (ITO) film pattern as a transparent electrode; after cleaning the glass substrate with ethanol, UV-ozone processing to obtain a pretreated glass substrate.

(2) Vacuum evaporation: vacuum evaporation of each layer is carried out on the pretreated glass substrate by vacuum evaporation method, and the treated glass substrate is placed in a vacuum evaporation chamber, and the degree of vacuum is ≤2×10 ^{− 4} Pa, the device structure is as follows: ITO/HAT-CN (10 nm)/TAPC (40 nm)/mCP (10 nm)/A (150 nm)/TMPYPB (45 nm)/LiF (1 nm)/Al (100 nm); the specific layer evaporation is a conventional technique.

(3) Device packaging: seal the fabricated organic electroluminescent device in a nitrogen atmosphere glove box with a water oxygen concentration of less than 1 ppm, and then cover the above-mentioned film formation with a sealing cover with epoxy UV-curable resin glass. The substrate is sealed by UV curing; the specific encapsulation is conventional technology.

Performance evaluation of organic electroluminescent devices with 150 nm material A as the light-emitting layer.

Direct current was applied to the fabricated organic electroluminescent device, and the luminescence performance was evaluated by using an integrating sphere; the current-voltage characteristics were measured by a computer-controlled Keithley 2400 digital source meter. The luminescence properties of the organic electroluminescent device were measured under the condition of changing the applied DC voltage. Device performance is shown in Table 1 and Figure 4.

Example 4 Fabrication and performance evaluation of an organic electroluminescent device with 200 nm material A as the light-emitting layer.

The fabrication steps of the organic electroluminescent device with 200 nm material A as the light-emitting layer are as follows.

(1) Pretreatment of glass anode: select a glass substrate (3×3 mm) with an indium tin oxide (ITO) film pattern as a transparent electrode; after cleaning the glass substrate with ethanol, UV-ozone processing to obtain a pretreated glass substrate.

(2) Vacuum evaporation: vacuum evaporation of each layer is carried out on the pretreated glass substrate by vacuum evaporation method, and the treated glass substrate is placed in a vacuum evaporation chamber, and the degree of vacuum is ≤2×10 ^{− 4} Pa, the device structure is as follows: ITO/HAT-CN (10 nm)/TAPC (40 nm)/mCP (10 nm)/A (200 nm)/TMPYPB (45 nm)/LiF (1 nm)/Al (100 nm); the specific layer evaporation is a conventional technique.

(3) Device packaging: seal the fabricated organic electroluminescent device in a nitrogen atmosphere glove box with a water oxygen concentration of less than 1 ppm, and then cover the above-mentioned film formation with a sealing cover with epoxy UV-curable resin glass. The substrate is sealed by UV curing; the specific encapsulation is conventional technology.

Performance evaluation of organic electroluminescent devices with 200 nm material A as the light-emitting layer.

Direct current was applied to the fabricated organic electroluminescent device, and the luminescence performance was evaluated by using an integrating sphere; the current-voltage characteristics were measured by a computer-controlled Keithley 2400 digital source meter. The luminescence properties of the organic electroluminescent device were measured under the condition of changing the applied DC voltage. Device performance is shown in Table 1 and Figure 4.

Comparative Example 1.

Fabrication and performance evaluation of organic electroluminescent devices with 100 nm compound B as the light-emitting layer (that is, only using compound B as the light-emitting layer).

The structural formula of compound B is as follows.

.

The fabrication steps of the organic electroluminescent device in which B is a light-emitting layer are as follows.

(1) Pretreatment of glass anode: select a glass substrate (3×3 mm) with an indium tin oxide (ITO) film pattern as a transparent electrode; after cleaning the glass substrate with ethanol, UV-ozone processing to obtain a pretreated glass substrate.

(2) Vacuum evaporation: vacuum evaporation of each layer is carried out on the pretreated glass substrate by vacuum evaporation method, and the treated glass substrate is placed in a vacuum evaporation chamber, and the degree of vacuum is ≤2×10 ^{− 4} Pa, the device structure is as follows. ITO/HAT-CN (10 nm)/TAPC (60 nm)/mCP (10 nm)/ B (100 nm)/TMPYPB (45 nm)/LiF (1 nm)/Al (100 nm); Plating is a conventional technique.

(3) Device packaging: seal the fabricated organic electroluminescent device in a nitrogen atmosphere glove box with a water oxygen concentration of less than 1 ppm, and then cover the above-mentioned film formation with a sealing cover with epoxy UV-curable resin glass. The substrate is sealed by UV curing; the specific encapsulation is conventional technology.

Performance evaluation of organic electroluminescent devices with 100 nm compound B as the light-emitting layer.

Direct current was applied to the fabricated organic electroluminescent device, and the luminescence performance was evaluated by using an integrating sphere; the current-voltage characteristics were measured by a computer-controlled Keithley 2400 digital source meter. The luminescence properties of the organic electroluminescent device were measured under the condition of changing the applied DC voltage. The device performance is shown in Figure 5. The turn-on voltage is 3.5 V, the maximum external quantum efficiency is 8.4%, and the electroluminescence peak is 525 nm.

Comparative example two.

Fabrication and performance evaluation of organic electroluminescent devices with 100 nm compound C as the light-emitting layer (that is, only using compound C as the light-emitting layer).

The structural formula of compound C is as follows.

.

The fabrication steps of the organic electroluminescent device in which B is a light-emitting layer are as follows.

(1) Pretreatment of glass anode: select a glass substrate (3×3 mm) with an indium tin oxide (ITO) film pattern as a transparent electrode; after cleaning the glass substrate with ethanol, UV-ozone processing to obtain a pretreated glass substrate.

(2) Vacuum evaporation: vacuum evaporation of each layer is carried out on the pretreated glass substrate by vacuum evaporation method, and the treated glass substrate is placed in a vacuum evaporation chamber, and the degree of vacuum is ≤2×10 ^{− 4} Pa, the device structure is as follows. ITO/HAT-CN (10 nm)/TAPC (60 nm)/mCP (10 nm)/C (100 nm)/TMPYPB (45 nm)/LiF (1 nm)/Al (100 nm); Plating is a conventional technique.

(3) Device packaging: seal the fabricated organic electroluminescent device in a nitrogen atmosphere glove box with a water oxygen concentration of less than 1 ppm, and then cover the above-mentioned film formation with a sealing cover with epoxy UV-curable resin glass. The substrate is sealed by UV curing; the specific encapsulation is conventional technology.

Performance evaluation of organic electroluminescent devices with 100 nm compound C as the light-emitting layer.

Direct current was applied to the fabricated organic electroluminescent device, and the luminescence performance was evaluated by using an integrating sphere; the current-voltage characteristics were measured by a computer-controlled Keithley 2400 digital source meter. The luminescence properties of the organic electroluminescent device were measured under the condition of changing the applied DC voltage. The device performance is shown in Figure 6, the turn-on voltage is 7.0 V, the maximum external quantum efficiency is 14.8%, and the electroluminescence peak is 514 nm.

.

Preparation of Compounds of Comparative Examples Methods for the preparation of compounds of reference examples were made. Obviously, the descriptions of the above embodiments are only used to help understand the method and the core idea of the present invention. It should be pointed out that for those of ordinary skill in the technical field, without departing from the principle of the present invention, several improvements and modifications can also be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention .

Claims (10)

1. An ultra-thick undoped electroluminescent device based on thermally activated delayed fluorescent material, wherein the thermally activated delayed fluorescent material is used as an ultra-thick undoped light-emitting layer, characterized in that: the chemical structural formula of the thermally activated delayed fluorescent material is as follows:

   

   .
2. The ultrathick undoped electroluminescent device based on thermally activated delayed fluorescent material according to claim 1, wherein the ultrathick undoped electroluminescent device based on thermally activated delayed fluorescent material is composed of anode, hole An injection layer, a hole transport layer, a blocking layer, an ultra-thick undoped light-emitting layer, an electron transport layer, an electron injection layer, and a cathode are composed.
3. The ultra-thick undoped electroluminescent device based on thermally activated delayed fluorescent material according to claim 1, wherein the thickness of the ultra-thick undoped light-emitting layer is 50-200 nm.
4. The ultra-thick undoped electroluminescent device based on a thermally activated delayed fluorescent material according to claim 1, wherein the ultra-thick undoped light-emitting layer is composed of the thermally activated delayed fluorescent material alone.
5. The ultrathick undoped electroluminescent device based on thermally activated delayed fluorescent material according to claim 1, characterized in that it is made of 2,3,4,5,6-pentafluorobenzonitrile, 3,6-di-tert-butylene Base-9H-carbazole and 9H-carbazole are used as raw materials, and the thermally activated delayed fluorescent material is prepared by the reaction.
6. The ultrathick undoped electroluminescent device based on thermally activated delayed fluorescent material according to claim 5, wherein the reaction is a continuous one-pot reaction; 2,3,4,5,6-pentafluorobenzonitrile, The molar ratio of 3,6-di-tert-butyl-9H-carbazole and 9H-carbazole is 1:3～3.5:2～2.5; the reaction is carried out in the presence of NaH and under nitrogen protection, and the temperature of the reaction is room temperature Or heating, the reaction time is 12 ~ 24 h.
7. The method for preparing an ultra-thick undoped electroluminescent device based on thermally activated delayed fluorescent material according to claim 1, characterized in that a hole injection layer, a hole transport layer, a blocking layer, an ultra-thick hole injection layer, a hole transport layer, a blocking layer, an ultra-thick hole injection layer, a hole transport layer, a super A thick undoped light-emitting layer, an electron transport layer, an electron injection layer, and a cathode are used to obtain the ultra-thick undoped electroluminescence device based on the thermally activated delayed fluorescent material.
8. The ultra-thick light-emitting layer of an electroluminescent device is characterized in that it is composed of the thermally activated delayed fluorescent material according to claim 1 alone.
9. The application of the ultra-thick light-emitting layer of the electroluminescent device of claim 8 in the preparation of the ultra-thick undoped electroluminescent device based on the thermally activated delayed fluorescent material of claim 1 .
10. Application of the ultrathick undoped electroluminescent device based on thermally activated delayed fluorescent material according to claim 1 in the preparation of electroluminescent device.